JPS58197409A - Control device for output of combined cycle plant - Google Patents

Abstract

PURPOSE:To prevent the exessively high thermal stress of a steam turbine side, by changing the flow of fuel within a control value of a load variation rate limiting signal from a steam cycle control device. CONSTITUTION:Combustion gas obtained by air from an air compressor 1 and fuel which are burnt in a burner 2, drives a gas turbine 3 producing exhaust gas which is led into a waste heat recovering boiler 4 generating steam for driving a steam turbine 5. Pulses (a) from a load setting device 11 are applied to a digital setting unit 18, and a D/A converter 19 converts the number of pulses from a pulse generator 17 into a digital signal and applies a load setting signal (1) to a load variation rate limiter 21 in which the deviation between the load setting signal (1) and a regulator valve open degree demand signal (p) is controlled by means of an integrator 24 so that the deviation has zero value, thereby the regulator open degree demand signal (p) moderately rises even if the load setting signal (1) abruptly rises.

Description

Detailed Description of the Invention [Technical Field of the Invention] The present invention relates to a combined system in which a gas turbine cycle and a steam turbine cycle are connected via an exhaust heat recovery mailer, and the gas turbine and the steam turbine are connected by a single shaft. This invention relates to an output control device for a cycle plant.

TECHNICAL BACKGROUND OF THE INVENTION This type of combined cycle plant is also called a uniaxial combined cycle plant, and is generally constructed as shown in FIG. That is, compressed air compressed by the air compressor I is mixed with fuel in the combustor to become high-temperature combustion gas, which drives the gas turbine J. The exhaust gas from the gas turbine 3 is led to an exhaust heat recovery boiler, where water in a drum (not shown) is heated to generate steam. Next, this steam is guided through a steam control valve /Q to a steam turbine j to drive it, and its exhaust gas is cooled by seawater or the like and becomes condensate. Further, the flow rate of the fuel supplied to the combustor is controlled by a fuel flow rate regulating valve 7.

Therefore, the air compressor 1, the combustion coco gas turbine 3, and the fuel flow rate regulating valve 7 form part of the gas turbine cycle referred to here as a steam turbine! The gas turbine 3 and the steam turbine bay drive the generator 6 in a state in which the gas turbine 3 and the steam turbine bay are connected to one shaft.

On the other hand, the temperature of the combustor is monitored by a combustor temperature monitoring device 9, and a temperature limit signal j is applied as one input of the low value priority circuit g. Further, an output control device 10 comprising a load setting device, a steam cycle control device, etc., which will be described later.
The regulating valve opening request signal k is applied as the other input of the low value priority circuit t, and the medium level low reserve signal of these signals is applied to the fuel flow regulator l1vI4 regulating valve 7, thereby reducing the flow to the combustor. Fuel supply is controlled.

Here, the configuration and operation of the output control device io will be explained with reference to FIGS. 1 and 3.

First, the output control device 10 includes a load setting device // that outputs a pulse signal a or b with a time width according to the installed layer value by setting the shaft output of the combined cycle plant, and a steam cycle control Mlii/- which outputs an analog signal C for limiting the rate of change of load increase;
A signal conversion device/3 that converts d into a pulse signal with a time width corresponding to its level, an inverter group that obtains a pulse signal with the level of which pulse signal d is inverted, and a logical product of the pulse signal company and... A module N that outputs a pulse signal f
The D circuit 1S and the ND circuit/A, which similarly performs the AND of the pulse signals S and , and output the pulse signal g, generate a pulse signal with a much higher frequency than the pulse signals a, b, or dK. Pulse generator/7 counts and counts up the pulses of the pulse generator 1 when the pulse signal f is at the rHJ level, and counts up the pulses of the pulse generator 17 when the pulse signal g is at the "■" level. and a digital setting device 7 such as a reversible counter that counts down, and converts the digital signal of this digital setting device /l into an analog signal for controlling the fuel flow rate regulating valve 7, that is, a regulating valve opening request signal k. A converter/?
It is made up of. Note that the pulse signal a of the load setting device l/ is a command to increase the load setting, and the pulse signal S is a command to lower the load setting.

Assume that the load setting device outputs the pulse signal 1 shown in Figure 113 (a) K, and the steam cycle control value position l outputs the analog signal e shown in Figure 113 (a) 6C. , the signal converter i, i has a narrow pulse width when this signal is at a low level, and on the contrary, a wide pulse width when it is at a %^ level. The same figure with signal d inverted (・)
The pulse signals shown in are output respectively. The AND circuit 13 takes the logical product of the pulse signals a and e, and applies the pulse signal f shown in FIG. When the pulse signal f is at [HJ level, the digital setter/l increases the number of pulses of the pulse signal shown in (k) in the same figure to 11. As shown in FIG. 1, it rises at a constant rate of change at time TI corresponding to the "H" level of the pulse signal f, and otherwise maintains a constant level.
Overall, a signal is generated which increases depending on the output signal eK of the steam cycle control station 1. That is, if the level of the output signal C of the steam cycle control station I is small, D
-The output signal of the D-M converter/'I increases rapidly, and conversely, when the level of the output signal C of the steam cycle control device l- is high, the output signal of the D-M converter/'I increases gradually. do.

Therefore, the output signal C of the steam cycle control station l
In response to the load setting increase command a of the load setting device //,
It acts as a charge rise suppression signal, and also acts as a load setting device/
It also acts as a load drop suppression signal for the load setting lowering command bK of /.

[Problems with background technology]

In this way, it is possible to prevent a sudden load increase on the steam turbine side at the time of starting up a combined cycle plant. The rate of change during 13 hours is exactly equal to the rate of change in the state where the inhibition signal of the steam cycle control device L- is not output, and in the process of increasing the load of the steam turbine, the pulse of the signal converter/J If the width is long, control is performed such that the load increases rapidly in a short period of time, and then the load is held constant for a relatively long period of time. When the load suddenly increases in -F in this way, excessive thermal stress acts on the steam turbine, which has the drawback of shortening the life of the steam turbine itself.

In addition, the output of the load setting device l/ is a pulse signal, and the analog signal of the steam cycle control device l is also converted into a pulse signal by the signal converter/J, and the AND circuit /k or 16 converts both of these pulse signals. Since the configuration is a logical product, there are disadvantages in that the coordination of the two pulse signals becomes uncoordinated and the rate of change in the load is restricted to a smaller value than necessary.

OBJECT OF THE INVENTION] Therefore, an object of the present invention is to provide a combined cycle plant that can prevent excessive thermal stress from acting on a steam turbine and can freely control the rate of load change within the limits of a steam cycle control device. The purpose of the present invention is to provide an output control device.

(Summary of the invention) In order to achieve the above object, the output control device for a combined cycle plant of the present invention sets the shaft output of the combined cycle plant, thereby controlling the time width according to the set value. A load setting device that outputs a pulse signal, a steam cycle control device that outputs an analog signal to limit the rate of load change of the steam turbine, and a steam cycle control device that receives the pulse signal of the load setting device as input and determines its pulse width. a signal conversion device that outputs an analog signal whose level changes at a speed corresponding to the output signal level of the steam cycle control device; a level limiter that passes a signal whose maximum level is limited according to the output signal level of the steam cycle control device; and the level limiter. an integrator for integrating an output signal of the spinning signal converter, and a deviation between the output signal of the spinning signal converter and the output signal of the integrator is added to the integrator via the level limiter. The fuel flow rate regulating valve of the gas turbine cycle is controlled by the output signal of the load change rate limiter.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to the accompanying drawings.

Figure 1 is a block diagram showing the configuration of an output control device for a combined cycle plant according to the present invention, in which parts given the same reference numerals as in the TS diagram indicate the same elements. Then, the signal converter [/, 7, inverter lda and mu ND circuit /j, /4 in Figure 1 are removed, and the negative # setting device Wit, // is directly connected to the digital setting device it. , a level limiter 23 for passing a signal whose maximum level is limited according to the output signal level of the subtractor 1 steam cycle control device 1, and this level limiter 23 are provided on the output side of the D-me converter 1. A new load change rate limiter is provided in which the output signal of the A converter/de and the output signal of the integrator are added to the subtraction S-. It is set in.

The operation of the output control device for a combined cycle plant of the present invention constructed as described above will be explained below.

First, a load setting increase command is issued from the load setting device L/L (
When the pulse signal a is digitally processed into @/f, the digital setter /I counts the number of pulses from the pulse generator 1 during the period when the pulse signal a is at the "H" level.

The D-mu converter/D converts this count value into a digital signal and applies the load setting signal l having a true shape as shown in FIG. 3(k) K to the load change rate limiter J/.

Next, the load change rate limiter 1 uses a subtracter to add the deviation n between the load setting signal j and the foot signal to the level limiter n. Depending on the level of the output signal C of the control device [,
Deviation nf) By limiting the I thick bell, the integrator 41
In addition to the integral l! This signal is integrated and used as the other input of the regulating valve opening request signal pt low value priority circuit l.

Note that this 14m valve opening request signal p is input to the "C# calculator" as a feedback signal m.

As is clear from this, the load change rate limiter K/ is controlled so that the deviation between the load setting signal l and the adjustment valve opening request signal p becomes zero through the integral operation of the integrator λ. At the same time, the maximum value of the deviation is limited by the output signal e of the steam cycle control station I, so even if
Even if the load setting signal l rises rapidly, the regulating valve opening request signal p rises gradually. ... Figure S shows the change in the regulating valve opening request signal of the conventional output control device 10 corresponding to the change in the load setting increase command a of the load setting device // and the J! of the output control device I of the present invention. ! This is a time chart that compares the changes in the valve opening request signal p with the conventional adjustment valve opening request signal, which repeatedly changes by rapidly rising in a short period of time and then remaining constant for a relatively long period of time. However, the 14 valve opening request signal p according to the present invention increases linearly in approximately proportion to the load setting increase command.

On the other hand, it is clear that the same effect as described above is carried out in response to the load setting increase command, and that there is a gradual drop in a straight line with respect to the valve adjustment degree requirement.

In the above embodiment, there is a distance K between the load setting device/l and the load change rate limiter, a digital setting device/I that determines the number of pulses of the pulse generator/i, and the output of this digital setting device/l. DA converter/l that converts into analog signal
However, the point is that any other signal conversion device can be used as long as it inputs the pulse signal of the load setting device // and outputs a signal whose level increases at a speed corresponding to the pulse width. Of course, it is also possible to use the above, and substantially the same effect as described above can be achieved by this as well.

〔Effect of the invention〕

As is clear from the above explanation, according to the output control device for a combined cycle plant of the present invention, the fuel flow iIk regulating valve can be controlled once continuously within the limit value of the load change rate limit signal from the steam cycle control device. This allows fuel to be supplied most efficiently.This also prevents the thermal stress on the steam turbine side from becoming excessive, and also prevents load changes from the D-me converter. Since both the signal l, which is the rate request, and the signal C, which limits the load change rate from the steam cycle control device, are analog signals, it is possible to freely set the load change rate within the steam cycle limit range. This excellent effect can be obtained.

[Brief explanation of the drawing]

Figure 1 is a system diagram showing the configuration of a typical combined cycle plant, Figure 1 is a block diagram showing the configuration of a conventional output control device that controls this combined cycle plant, and Figure 3 is the operation of the output control device. Figure Y is a block diagram showing the configuration of an embodiment of the output control device for a combined cycle plant according to the present invention, and Figure S is a time chart for explaining the operation of the embodiment. It is. /... Air compressor, K... Combustor, 3... Gas turbine, D... Exhaust heat recovery boiler, j... Steam turbine, 6... Generator, 7... Fuel flow rate Adjustment valve, g...
Low value priority circuit, V... phosphor temperature monitoring device, 10.
X)... Output control device, /... Load setting device, /...
...Steam cycle control device, 13...Signal conversion device,
lda...inverter, /r. /6・AND circuit, /7...pulse generator, /l...
・Digital setting device, /9・-・D-A converter, −/・
...Load change rate limiter, -1...Subtractor, Ko3...
Level limiter, -da...integral di. Applicant's agent Kiyoshi Inomata

Claims (1)

[Claims] In an output control device for a combined cycle plant in which a gas turbine cycle and a steam turbine cycle are connected via an exhaust heat recovery boiler, and the gas turbine and the steam turbine are connected by a single shaft. , by setting the export power of the combined cycle plant, a load setting device outputs a pulse signal with a time width corresponding to the set value, and an analog signal for limiting the load change rate of the bi-injected steam turbine. a steam cycle control device that outputs a signal, a signal conversion device that receives a pulse signal from the load setting device and outputs an analog signal whose level changes at a speed corresponding to the pulse width, and a steam cycle control device that outputs a level limiter that passes a signal whose maximum level is limited according to the output signal level of the signal converter, and an integrator that integrates the output signal of the level limiter, the output signal of the signal converter and the output signal of the integrator. The deviation from ^11ffi level limiter is [
a load change rate limiter applied to the integrator, and configured to control the fuel flow rate-valve regulation of the gas turbine cycle by the output signal of the load change rate limiter. Output control device for a combined cycle plant that produces mold.